Installing APC Cache and setting up in Magento

http://www.euperia.com/website-performance-2/how-to-add-apc-cache-to-magento/799

http://magento2x.com/apc-configuration-for-magento/

http://www.aitoc.com/en/blog/apc_speeds_up_Magento.html

http://www.magentocommerce.com/boards/viewthread/8937/P45/
http://www.designguru.org/blog/120810/how-install-apc-media-temples-gridserver-accounts